1. Field of the Invention
The present invention relates to an apparatus for measuring levels of materials, especially of fluids, and optionally for calculating a density profile of a mixed fluid system.
2. Description of the Related Art
A density profiler has been described in WO2000/022387. The device comprises a linear array of sources of ionising radiation which emit radiation towards detectors disposed in one or more linear arrays. When the source array and detector array(s) are positioned so that they traverse the interfaces between two or more fluids in a container, the interfaces of the fluids may be identified from the differences in radiation received by each detector in the array. The device has been successfully deployed for use in storage tanks and oil separators. A desirable feature of the profiler device is its compact diameter which enables it to be fitted into a vessel through a standard access port. In some circumstances it is desirable to reduce the cross-section of the profiler device even more in order to access installations in which the size of the port or the space around the port makes installation particularly difficult. Also the reduction in size of the detector arrays can allow thicker dip pipes or additional thicknesses of insulating materials to be used. It is therefore an object of the invention to provide a density profiler in which the detector array(s) are relatively small compared with known devices.